Functional MRI (fMRI) has become a dominant tool in the physiological studies of human cognition and behavior. The moment- to-moment signaling within the brain, however, is understood to be fundamentally electrical. Despite over a decade of applied fMRI research the precise relationship the vascular signals in fMRI and the electrical activity of the brain is largely unknown. In this CEBRA application, we propose to complete development of our methods of simultaneous EEG and fMRI and to adapt these to the recording of extracellular potentials. We believe that we have come up with robust solutions for recording microVolt EEG signals in the presence of milliVolt MR-generated artifacts and are now prepared to enter a development phase for this technology during which we can complete the construction of apparatus appropriate for human research applications. It has long been clear that the problems of concurrent EEG and fMRI are similar to those in concurrent extracellular recording and fMRIas the sources of artifacts are essentially the same. In fact, the signal to noise ratio for the latter should be somewhat better. There are however, significant hurdles to overcome in studying and controlling the safety of such recordings, which are the focus of much of this grant proposal. We believe that this is an exceptionally significant project, in that these tools will enable us to perform crucial validation experiments that will be important in firming the very foundations on which the interpretation of functional MRI is based. Within the limited confines of the budget for the CEBRA program, the project will stop short of actual human experimentation with depth electrodes - the human work will be limited to scalp EEG to stay within the limited scope of the stage I mechanism. On its successful completion, the project will be followed immediately by an application for Stage II support to begin animal experimentation and shortly thereafter to initiate human studies.